Wayne Rooney’s desire to walk out on Manchester United has left the Premier League club facing the loss of a third world-class attacker in two years.

Manager Alex Ferguson said he was “dumbfounded” at the decision of Wayne Rooney not to enter into negotiations about extending his contract beyond the summer of 2012. “We just don’t know what’s changed the boy’s mind… I was shocked,” Ferguson said. “I had a meeting with the boy and he reiterated what his agent had said. He wanted to go.”

Rooney has become most marketable asset at United since the acquisition of Portugal forward Cristiano Ronaldo to Real Madrid for $125 million in June 2009. The same summer, Carlos Tevez left the 18-time champions to join cross-town rival Manchester City, one of the few clubs that would be able to afford the wages the 24-year-old Rooney will demand.

The prospect the reigning soccer player of the year in England leaving United would have seemed unthinkable last season, when Rooney scored 34 goals in the Premier League to establish himself as one of the top players.

But his form this season has dipped dramatically and his private life became the subject of newspaper allegations that he had repeatedly cheated on his then-pregnant wife with a prostitute.

Having said in March that he was prepared to sign for United “for life,” Rooney is looking for an escape route from Old Trafford, which may come in January before his transfer value plummets.

“I was in the office on Aug. 14 when [United chief executive] David Gill told me he’d had a call from his agent saying that Wayne wasn’t going to sign his contract,” Ferguson said.

“He said he couldn’t believe it and neither could I. I was dumbfounded, I couldn’t understand it at all because only months before he’d said he was at the biggest club in the world.”

Following the allegations about his private life, Ferguson benched Rooney for the next game against Everton — the club who traded him to United for more than $40 million in 2004 — to shield him the fans’ abuse. However, Rooney has continued to see limited playing time since, with Ferguson saying an ankle injury forced him to miss several games.